Kinetics of Space-Confined Inverse Temperature Crystallization: Gradients Enlarge Thin Perovskite Single Crystals

Space-confined inverse temperature crystallization (SC-ITC) is a prevalent technique for fabricating single-crystal perovskite solar cells, but its kinetics remain to be understood to increase the size of perovskite thin crystals, which are currently small and challenging to manage. Here we equipped SC-ITC with a camera to monitor its kinetics and found that the limitations on crystal size stem primarily from restricted solute diffusion and competing nucleation. To address these issues, we employed gradients in solution thickness to enhance solute transport and in temperature to mitigate competing nucleation. This led to a 4-fold increased size of the crystals up to 19 mm 2, growth velocity up to 34 μm min –1, and solute flux up to 1.65 × 10 –5 g mm –2 min –1 . We explored the application of these crystals in X-ray-voltaics, achieving 1% power conversion efficiency under 40 keV X-ray radiation, showcasing their potential for energy harvesting in space and nuclear waste facilities.